Artist’s view of BepiColombo at Mercury

BepiColombo is an especially challenging mission because Mercury's orbit is very close to the Sun. This makes the planet difficult to observe from a distance, because the Sun is so bright. Furthermore, it is difficult to reach it and to place a spacecraft in a stable orbit around it, due to the gravity of the Sun. Scientists want to study Mercury because of the valuable clues it can provide about how planets form and interact with the Sun.

Only NASA's Mariner 10 and MESSENGER have visited Mercury so far. Mariner 10 provided the first-ever close-up images of the planet when it flew past three times in 1974-1975. En route to its final destination in orbit around Mercury in 2011, MESSENGER flew past the planet on 14 January 2008, providing new data and images. Once BepiColombo arrives in 2019, it will help reveal information on the composition and history of Mercury and the history and formation of the inner planets in general, including Earth.

With two spacecraft, BepiColombo is a large and costly mission - it is one of the 'cornerstones' in ESA's long-term science programme. The mission presents enormous, but exciting challenges.
 
 
Spacecraft
 
The BepiColombo mission is based on two spacecraft:

• a Mercury Planetary Orbiter (MPO); and
• a Mercury Magnetospheric Orbiter (MMO)

Among several investigations, BepiColombo will make a complete map of Mercury at different wavelengths. This will allow to map the planet's mineralogy and elemental composition and determine whether the interior of the planet is molten or not.
 
 
Journey
 
Several launch methods have been extensively studied. In the selected scenario, for its journey to destination BepiColombo will cleverly use the gravity of the Moon, Earth, Venus and Mercury itself in combination with the thrust provided by solar-electric propulsion (SEP). During the voyage to Mercury, the two orbiters and transfer module, consisting of electric propulsion and chemical propulsion units, will form one single composite spacecraft.

When approaching Mercury, the transfer module will be separated and the composite spacecraft will use conventional rocket engines and the so-called 'weak stability boundary capture technique' to bring it into polar orbit around the planet. When the MMO orbit is reached, the MPO will separate and lower its altitude by means of chemical propulsion to its operational orbit. Observations from orbit will go on for one Earth year.
 
 
History
 
As the nearest planet to the Sun, Mercury has an important role in showing us how planets form. Mercury, Venus, Earth and Mars make up the family of terrestrial planets, each carrying essential information to trace the history of the whole group.

The knowledge of how they originated and evolved is a key to understanding how conditions supporting life arose in the Solar System, and possibly elsewhere. As long as Earth-like planets orbiting other stars remain inaccessible to astronomers, the Solar System is the only laboratory where scientists can test models applicable to other planetary systems.

Exploring Mercury is therefore fundamental to answer important astrophysical and philosophical questions such as 'Are Earth-like planets common in the Galaxy?'

A European mission to Mercury was first proposed in May 1993. Although an assessment showed it to be too costly for a medium-size mission, ESA made a Mercury orbiter one of the three new Cornerstones missions when the Horizon 2000 science programme was extended in 1994.

Gaia competed with BepiColombo for the fifth Cornerstone mission. In October 2000, ESA approved a package of missions for 2008–2013 and both BepiColombo and Gaia were approved.
 
 
Partnerships
 
BepiColombo is a joint mission between ESA and the Japanese Aerospace Exploration Agency (JAXA), executed under ESA leadership.
 
 
Last update: 19 August 2009